text: The first known use of liquation on a large scale was in Germany in the mid-15th century. Metal workers had long known that Central European copper ore was rich in silver, so it was only a matter of time until a method was discovered that could separate the two metals.
  Liquation is first documented in the archives of the municipal foundry in Nuremberg in 1453. Nuremberg was one of Germany's main centres of metal refining and fabrication, and was a leader in metallurgical techniques. Five liquation plants soon sprang up around the city, and within 15 years had spread throughout Germany, Poland and the Italian Alps.
  This is often regarded as the beginning of liquation, but evidence suggests liquation may have existed in smaller-scale use centuries earlier. The sophisticated nature of the 15th century liquation plants with custom-made furnaces would be surprising for a new technology. There was also a far simpler but more labour-intensive version of the method brought to Japan by the Portuguese in 1591; this is possibly the remnants of an earlier European method.
  Agricola discusses various types of copper produced from the liquation process; one of these is caldarium or ‘cauldron copper’ which contains a high level of lead and was used to make medieval cauldrons. Analysis of 13th century cauldrons shows that they are made out of copper with a low level of silver and high levels of lead which would match that produced by liquation.
  Liquation may even have existed as early as the 12th century; in Theophilus’ On Divers Arts he makes a possible reference to liquation. However, he was not an expert in metallurgy, so his writings may not be accurate, and though there were similar cauldrons in the 12th century, no compositional analysis has been published that supports this theory.
  Against the idea that this process was used significantly before it became widespread in the mid-15th century, is the fact that it had to be done on a large-scale to be financially viable. There is no evidence of large-scale liquation before Nuremberg. Also, efficient liquation requires an extremely skilled practitioner. Anyone with that much skill is unlikely to spend much time on something unprofitable.
  Some suggest liquation existed even earlier. Babylonian texts from Mari mention that ‘mountain copper’ was ‘washed’ to produce ‘washed copper’ and that lead was used with silver to produce ‘washed silver’. Some say this shows liquation was being carried out in the Near East as early as the second millennium BC. Crucially, however, these texts do not specifically mention lead being used with copper to produce silver, as would be expected for liquation.